In the next generation of networks, there is a need for a communication node to move frequently, and when the communication node moves, its address is typically changed. During communication with a mobile communication node, the communication node has to be located. In other words, an identifier of the communication node, such as a Fully Qualified Domain Name (FQDN) or an identification address, has to be converted into a network address which is accessible through communication by the present communication node.
An existing method for locating a mobile communication node is locating by mobile Internet Protocol (IP). This method is described briefly here with respect to the mobile IPv6.
Based upon technologies supporting node mobility in the IPv4, the method proposes technologies supporting communication node mobility in an IPv6 network.
FIG. 1 illustrates a schematic diagram of a principle of the method. A mobile node 110 moves from a home network to a foreign network. The following operations will be performed during its moving.
1. The mobile node 110 obtains in the foreign network a mobile address through an address configuration mechanism.
2. The mobile node 110 sends an address binding message to a home agent 120, registering the newly obtained mobile address (a primary Care-of Address) with the home agent 120 of a home link. The home agent 120 makes the mobile address newly obtained by the mobile node 110 to be corresponded to a local address of the mobile node 110 and stores the correspondence, thereby accomplishing a binding registration function for the node, and then returns in response a “Binding Acknowledgement” message to the mobile node 110.
The following operations will be performed when a node 130 is to communication with the mobile node 110.
1. The node 130 sends a data packet, which is to be sent to the mobile node 110, to the home agent 120.
2. The home agent 120 forwards the data packet to the mobile node 110 through an extended routing head of the data packet.
3. The mobile node 110 sends to the node 130 the address binding message informing the node 130 of its new address.
4. If the node 130 supports the mechanism of the method, it creates a binding buffer dependent upon the received new address of the mobile node 110, and conducts subsequent communication directly with the mobile node 110 by use of information of this buffer. Otherwise, it keeps on sending a subsequent packet to the home address of the mobile node 110, and the home agent 120 over the home link of the mobile node 110 relays the data to the current primary Care-of Address of the mobile node 110.
A node in communication with a mobile node is referred to as a communication node of the mobile node, which may be a fixed node or a mobile node. The mobile node can provide its communication node with information of its current location.
There are two modes for communication between a mobile node and a communication node.
The first mode is a bidirectional tunnel mode.
This mode is available when the mobile node has not registered current binding information with the communication node. In this communication mode, a data packet sent from the communication node to the mobile node is routed to a home agent of the mobile node, and then reaches the mobile node through a tunnel. Data packet sent from the mobile node to the communication node is passed to the home agent through the tunnel, and the home agent routes the data packet to the communication node in a normal way. In this mode, the home agent intercepts any data packet sent to a home address of the mobile node in an agent neighbor way. Each intercepted data packet is tunneled to a primary Care-of Address of the mobile node. The bidirectional tunnel in this mode is implemented with IPv6 encapsulation.
The second mode is an optimized routing mode.
This mode requires the mobile node to register its current binding information with the communication node. In this communication mode, data packet sent from the communication node to the mobile node is routed directly to the primary Care-of Address of the mobile node. When the communication node is to send any data packet to an IPv6 destination, a binding buffered entry of the destination of the data packet will be detected. If the binding buffered entry of the destination is found, the communication node adds a new IPv6 routing head type, sets a destination address in an IP head as the primary Care-of Address of the mobile node designated in the binding buffered entry, and routes the data packet to the mobile node through the shortest path. This mode reduces congestion of the home agent and the home link of the mobile node, and also reduces an influence of a possible transmission failure on the home agent or the home link.
As can be seen from the above, a key of the locating method of the mobile IPv6 lies in that the home agent makes the primary Care-of Address be bound with the home address of the mobile node and stores the bonding upon reception of a binding update message, including the primary Care-of Address, sent by the mobile node from a new network. A change of an address of the mobile node is transparent to the communication node. In the optimized routing mode, the mobile node sends the binding update message to the communication node, and makes the home address of the mobile node to be corresponded to the current primary Care-of Address by use of a destination binding buffer in the communication node.
The above locating method of the mobile IPv6 is disadvantageous in that the method requires participation of the home agent, and a problem of triangular routing occurs when adopting the bidirectional tunnel mode. In this method, the home agent not only enables the locating of the communication node, but also participates in the forwarding of the data. The requirements on network devices are relatively strict. Further, a home agent is required to be deployed over each link, and all mobile terminals are required to implement mobile IP technologies, the requirements of which to the terminals are relatively strict.
Another existing method for locating a mobile communication node is registration locating of the Session Initiation Protocol (SIP).
According to this method, the SIP protocol is firstly required to be implemented in both a communication node and a mobile node. When the communication node is to communication with the mobile node, the communication node registers with an SIP server in a new network of the mobile node, and this SIP registration server can find a home domain of the mobile node through an SIP Universal Resource Identifier (SIP URI) of a user, and informs the SIP server of the home domain of the communication node about network parameters of the mobile node. Therefore, the communication node finds the network parameters of the mobile node through inquiring about the SIP server of its user home domain, and determines current location of the mobile node dependent upon the acquired network address parameters.
This method is disadvantageous in that the SIP protocol is a high level protocol developed for transmission of a media stream in a Packet-based network. Although the use of the SIP protocol can implement locating of the user, it is required that relevant network elements with architecture of the SIP protocol must be deployed in the network. The SIP protocol is required to be implemented in all network nodes, which may be unreasonable for many terminals which do not rely on the SIP protocol for communication. This method leads to both a high cost of network deployment and strict requirements on the communication nodes.